18d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===- InstCombineLoadStoreAlloca.cpp -------------------------------------===// 28d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 38d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// The LLVM Compiler Infrastructure 48d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 58d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// This file is distributed under the University of Illinois Open Source 68d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// License. See LICENSE.TXT for details. 78d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 88d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===----------------------------------------------------------------------===// 98d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// This file implements the visit functions for load, store and alloca. 118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner// 128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner//===----------------------------------------------------------------------===// 138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "InstCombine.h" 158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/IntrinsicInst.h" 16dd9344f3face8f1978a7f9f393c31b628144d1f6Dan Gohman#include "llvm/Analysis/Loads.h" 178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Target/TargetData.h" 188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Transforms/Utils/BasicBlockUtils.h" 198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/Transforms/Utils/Local.h" 208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner#include "llvm/ADT/Statistic.h" 218d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerusing namespace llvm; 228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 23ec68f552f2a5c1df10813a80929995185eb98243Chandler CarruthSTATISTIC(NumDeadStore, "Number of dead stores eliminated"); 24ec68f552f2a5c1df10813a80929995185eb98243Chandler CarruthSTATISTIC(NumGlobalCopies, "Number of allocas copied from constant global"); 25ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 26ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// pointsToConstantGlobal - Return true if V (possibly indirectly) points to 27ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// some part of a constant global variable. This intentionally only accepts 28ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// constant expressions because we can't rewrite arbitrary instructions. 29ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruthstatic bool pointsToConstantGlobal(Value *V) { 30ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 31ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return GV->isConstant(); 32ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 33ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CE->getOpcode() == Instruction::BitCast || 34ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth CE->getOpcode() == Instruction::GetElementPtr) 35ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return pointsToConstantGlobal(CE->getOperand(0)); 36ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return false; 37ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth} 38ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 39ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// isOnlyCopiedFromConstantGlobal - Recursively walk the uses of a (derived) 40ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// pointer to an alloca. Ignore any reads of the pointer, return false if we 41ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// see any stores or other unknown uses. If we see pointer arithmetic, keep 42ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// track of whether it moves the pointer (with IsOffset) but otherwise traverse 43ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// the uses. If we see a memcpy/memmove that targets an unoffseted pointer to 44ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// the alloca, and if the source pointer is a pointer to a constant global, we 45ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// can optimize this. 46ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruthstatic bool 47ec68f552f2a5c1df10813a80929995185eb98243Chandler CarruthisOnlyCopiedFromConstantGlobal(Value *V, MemTransferInst *&TheCopy, 48ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth SmallVectorImpl<Instruction *> &ToDelete, 49ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth bool IsOffset = false) { 50ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // We track lifetime intrinsics as we encounter them. If we decide to go 51ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // ahead and replace the value with the global, this lets the caller quickly 52ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // eliminate the markers. 53ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 54ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI!=E; ++UI) { 55ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth User *U = cast<Instruction>(*UI); 56ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 57ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (LoadInst *LI = dyn_cast<LoadInst>(U)) { 58ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // Ignore non-volatile loads, they are always ok. 59ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (!LI->isSimple()) return false; 60ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 61ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 62ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 63ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (BitCastInst *BCI = dyn_cast<BitCastInst>(U)) { 64ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If uses of the bitcast are ok, we are ok. 65ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (!isOnlyCopiedFromConstantGlobal(BCI, TheCopy, ToDelete, IsOffset)) 66ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return false; 67ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 68ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 69ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) { 70ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If the GEP has all zero indices, it doesn't offset the pointer. If it 71ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // doesn't, it does. 72ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (!isOnlyCopiedFromConstantGlobal(GEP, TheCopy, ToDelete, 73ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth IsOffset || !GEP->hasAllZeroIndices())) 74ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return false; 75ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 76ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 77ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 78ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CallSite CS = U) { 79ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If this is the function being called then we treat it like a load and 80ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // ignore it. 81ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CS.isCallee(UI)) 82ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 83ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 84ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If this is a readonly/readnone call site, then we know it is just a 85ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // load (but one that potentially returns the value itself), so we can 86ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // ignore it if we know that the value isn't captured. 87ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth unsigned ArgNo = CS.getArgumentNo(UI); 88ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CS.onlyReadsMemory() && 89ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth (CS.getInstruction()->use_empty() || CS.doesNotCapture(ArgNo))) 90ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 91ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 92ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If this is being passed as a byval argument, the caller is making a 93ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // copy, so it is only a read of the alloca. 94ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CS.isByValArgument(ArgNo)) 95ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 96ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 97ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 98ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // Lifetime intrinsics can be handled by the caller. 99ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(U)) { 100ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (II->getIntrinsicID() == Intrinsic::lifetime_start || 101ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth II->getIntrinsicID() == Intrinsic::lifetime_end) { 102ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth assert(II->use_empty() && "Lifetime markers have no result to use!"); 103ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth ToDelete.push_back(II); 104ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 105ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 106ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 107ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 108ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If this is isn't our memcpy/memmove, reject it as something we can't 109ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // handle. 110ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth MemTransferInst *MI = dyn_cast<MemTransferInst>(U); 111ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (MI == 0) 112ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return false; 113ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 114ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If the transfer is using the alloca as a source of the transfer, then 115ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // ignore it since it is a load (unless the transfer is volatile). 116ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (UI.getOperandNo() == 1) { 117ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (MI->isVolatile()) return false; 118ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth continue; 119ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 120ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 121ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If we already have seen a copy, reject the second one. 122ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (TheCopy) return false; 123ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 124ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If the pointer has been offset from the start of the alloca, we can't 125ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // safely handle this. 126ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (IsOffset) return false; 127ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 128ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If the memintrinsic isn't using the alloca as the dest, reject it. 129ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (UI.getOperandNo() != 0) return false; 130ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 131ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // If the source of the memcpy/move is not a constant global, reject it. 132ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (!pointsToConstantGlobal(MI->getSource())) 133ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return false; 134ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 135ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // Otherwise, the transform is safe. Remember the copy instruction. 136ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth TheCopy = MI; 137ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 138ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return true; 139ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth} 140ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 141ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// isOnlyCopiedFromConstantGlobal - Return true if the specified alloca is only 142ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// modified by a copy from a constant global. If we can prove this, we can 143ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// replace any uses of the alloca with uses of the global directly. 144ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruthstatic MemTransferInst * 145ec68f552f2a5c1df10813a80929995185eb98243Chandler CarruthisOnlyCopiedFromConstantGlobal(AllocaInst *AI, 146ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth SmallVectorImpl<Instruction *> &ToDelete) { 147ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth MemTransferInst *TheCopy = 0; 148ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (isOnlyCopiedFromConstantGlobal(AI, TheCopy, ToDelete)) 149ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return TheCopy; 150ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return 0; 151ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth} 152ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 153ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// getPointeeAlignment - Compute the minimum alignment of the value pointed 154ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth/// to by the given pointer. 155ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruthstatic unsigned getPointeeAlignment(Value *V, const TargetData &TD) { 156ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (ConstantExpr *CE = dyn_cast<ConstantExpr>(V)) 157ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (CE->getOpcode() == Instruction::BitCast || 158ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth (CE->getOpcode() == Instruction::GetElementPtr && 159ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth cast<GEPOperator>(CE)->hasAllZeroIndices())) 160ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return getPointeeAlignment(CE->getOperand(0), TD); 161ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 162ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (GlobalVariable *GV = dyn_cast<GlobalVariable>(V)) 163ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (!GV->isDeclaration()) 164ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return TD.getPreferredAlignment(GV); 165ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 166ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (PointerType *PT = dyn_cast<PointerType>(V->getType())) 167ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return TD.getABITypeAlignment(PT->getElementType()); 168ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 169ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return 0; 170ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth} 1718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1728d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitAllocaInst(AllocaInst &AI) { 17305d62537276197b3351d9887f4967590b6a3b901Dan Gohman // Ensure that the alloca array size argument has type intptr_t, so that 17405d62537276197b3351d9887f4967590b6a3b901Dan Gohman // any casting is exposed early. 17505d62537276197b3351d9887f4967590b6a3b901Dan Gohman if (TD) { 176db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *IntPtrTy = TD->getIntPtrType(AI.getContext()); 17705d62537276197b3351d9887f4967590b6a3b901Dan Gohman if (AI.getArraySize()->getType() != IntPtrTy) { 17805d62537276197b3351d9887f4967590b6a3b901Dan Gohman Value *V = Builder->CreateIntCast(AI.getArraySize(), 17905d62537276197b3351d9887f4967590b6a3b901Dan Gohman IntPtrTy, false); 18005d62537276197b3351d9887f4967590b6a3b901Dan Gohman AI.setOperand(0, V); 18105d62537276197b3351d9887f4967590b6a3b901Dan Gohman return &AI; 18205d62537276197b3351d9887f4967590b6a3b901Dan Gohman } 18305d62537276197b3351d9887f4967590b6a3b901Dan Gohman } 18405d62537276197b3351d9887f4967590b6a3b901Dan Gohman 1858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Convert: alloca Ty, C - where C is a constant != 1 into: alloca [C x Ty], 1 1868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (AI.isArrayAllocation()) { // Check C != 1 1878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (const ConstantInt *C = dyn_cast<ConstantInt>(AI.getArraySize())) { 188db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *NewTy = 1898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ArrayType::get(AI.getAllocatedType(), C->getZExtValue()); 1908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner AllocaInst *New = Builder->CreateAlloca(NewTy, 0, AI.getName()); 1918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner New->setAlignment(AI.getAlignment()); 1928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Scan to the end of the allocation instructions, to skip over a block of 1948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // allocas if possible...also skip interleaved debug info 1958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 1968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator It = New; 1978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner while (isa<AllocaInst>(*It) || isa<DbgInfoIntrinsic>(*It)) ++It; 1988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 1998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now that I is pointing to the first non-allocation-inst in the block, 2008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // insert our getelementptr instruction... 2018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 2028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *NullIdx =Constant::getNullValue(Type::getInt32Ty(AI.getContext())); 2038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Idx[2]; 2048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idx[0] = NullIdx; 2058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idx[1] = NullIdx; 206e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman Instruction *GEP = 207a9203109f4ac95aa7e9624f2838e3d89623ec902Jay Foad GetElementPtrInst::CreateInBounds(New, Idx, New->getName()+".sub"); 208e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman InsertNewInstBefore(GEP, *It); 2098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now make everything use the getelementptr instead of the original 2118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // allocation. 212e6f364b6c44eda14cd4ad54366ea5cc7246b9500Eli Friedman return ReplaceInstUsesWith(AI, GEP); 2138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else if (isa<UndefValue>(AI.getArraySize())) { 2148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(AI, Constant::getNullValue(AI.getType())); 2158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 21891fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (TD && AI.getAllocatedType()->isSized()) { 2198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the alignment is 0 (unspecified), assign it the preferred alignment. 2208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (AI.getAlignment() == 0) 2218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner AI.setAlignment(TD->getPrefTypeAlignment(AI.getAllocatedType())); 22291fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands 22391fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // Move all alloca's of zero byte objects to the entry block and merge them 22491fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // together. Note that we only do this for alloca's, because malloc should 22591fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // allocate and return a unique pointer, even for a zero byte allocation. 22691fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (TD->getTypeAllocSize(AI.getAllocatedType()) == 0) { 22791fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // For a zero sized alloca there is no point in doing an array allocation. 22891fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // This is helpful if the array size is a complicated expression not used 22991fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // elsewhere. 23091fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (AI.isArrayAllocation()) { 23191fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands AI.setOperand(0, ConstantInt::get(AI.getArraySize()->getType(), 1)); 23291fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands return &AI; 23391fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands } 23491fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands 23591fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // Get the first instruction in the entry block. 23691fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands BasicBlock &EntryBlock = AI.getParent()->getParent()->getEntryBlock(); 23791fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands Instruction *FirstInst = EntryBlock.getFirstNonPHIOrDbg(); 23891fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (FirstInst != &AI) { 23991fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // If the entry block doesn't start with a zero-size alloca then move 24091fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // this one to the start of the entry block. There is no problem with 24191fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // dominance as the array size was forced to a constant earlier already. 24291fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands AllocaInst *EntryAI = dyn_cast<AllocaInst>(FirstInst); 24391fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (!EntryAI || !EntryAI->getAllocatedType()->isSized() || 24491fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands TD->getTypeAllocSize(EntryAI->getAllocatedType()) != 0) { 24591fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands AI.moveBefore(FirstInst); 24691fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands return &AI; 24791fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands } 24891fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands 24991fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // Replace this zero-sized alloca with the one at the start of the entry 25091fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // block after ensuring that the address will be aligned enough for both 25191fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands // types. 25291fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands unsigned MaxAlign = 25391fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands std::max(TD->getPrefTypeAlignment(EntryAI->getAllocatedType()), 25491fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands TD->getPrefTypeAlignment(AI.getAllocatedType())); 25591fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands EntryAI->setAlignment(MaxAlign); 25691fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands if (AI.getType() != EntryAI->getType()) 25791fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands return new BitCastInst(EntryAI, AI.getType()); 25891fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands return ReplaceInstUsesWith(AI, EntryAI); 25991fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands } 260ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 261ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth } 262ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth 263ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // Check to see if this allocation is only modified by a memcpy/memmove from 264ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // a constant global whose alignment is equal to or exceeds that of the 265ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // allocation. If this is the case, we can change all users to use 266ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // the constant global instead. This is commonly produced by the CFE by 267ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // constructs like "void foo() { int A[] = {1,2,3,4,5,6,7,8,9...}; }" if 'A' 268ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth // is only subsequently read. 269ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth SmallVector<Instruction *, 4> ToDelete; 270ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (MemTransferInst *Copy = isOnlyCopiedFromConstantGlobal(&AI, ToDelete)) { 271ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth if (AI.getAlignment() <= getPointeeAlignment(Copy->getSource(), *TD)) { 272ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth DEBUG(dbgs() << "Found alloca equal to global: " << AI << '\n'); 273ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth DEBUG(dbgs() << " memcpy = " << *Copy << '\n'); 274ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth for (unsigned i = 0, e = ToDelete.size(); i != e; ++i) 275ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth EraseInstFromFunction(*ToDelete[i]); 276ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth Constant *TheSrc = cast<Constant>(Copy->getSource()); 277ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth Instruction *NewI 278ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth = ReplaceInstUsesWith(AI, ConstantExpr::getBitCast(TheSrc, 279ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth AI.getType())); 280ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth EraseInstFromFunction(*Copy); 281ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth ++NumGlobalCopies; 282ec68f552f2a5c1df10813a80929995185eb98243Chandler Carruth return NewI; 28391fa1da2f73ce77d386cacb1a69f38dcdf7cd60cDuncan Sands } 2848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 2858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 28678f8ef42173a3a9867ed789073d4ddc652fb7ff2Nuno Lopes // At last, use the generic allocation site handler to aggressively remove 28778f8ef42173a3a9867ed789073d4ddc652fb7ff2Nuno Lopes // unused allocas. 28878f8ef42173a3a9867ed789073d4ddc652fb7ff2Nuno Lopes return visitAllocSite(AI); 2898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 2908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 2928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineLoadCast - Fold 'load (cast P)' -> cast (load P)' when possible. 2938d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineLoadCast(InstCombiner &IC, LoadInst &LI, 2948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const TargetData *TD) { 2958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(LI.getOperand(0)); 2968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 2978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 298db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *DestTy = cast<PointerType>(CI->getType()); 299db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = DestTy->getElementType(); 300db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType())) { 3018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the address spaces don't match, don't eliminate the cast. 3038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (DestTy->getAddressSpace() != SrcTy->getAddressSpace()) 3048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 306db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 3078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3081df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (DestPTy->isIntegerTy() || DestPTy->isPointerTy() || 3091df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands DestPTy->isVectorTy()) { 3108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 3118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 3128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 313db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (ArrayType *ASrcTy = dyn_cast<ArrayType>(SrcPTy)) 3148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *CSrc = dyn_cast<Constant>(CastOp)) 3158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ASrcTy->getNumElements() != 0) { 3168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Idxs[2]; 3178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[0] = Constant::getNullValue(Type::getInt32Ty(LI.getContext())); 3188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Idxs[1] = Idxs[0]; 3198908ff207d8dc0daccde3dc5710dc805ec98e1faJay Foad CastOp = ConstantExpr::getGetElementPtr(CSrc, Idxs); 3208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = cast<PointerType>(CastOp->getType()); 3218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = SrcTy->getElementType(); 3228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (IC.getTargetData() && 3251df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isIntegerTy() || SrcPTy->isPointerTy() || 3261df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands SrcPTy->isVectorTy()) && 3278d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do not allow turning this into a load of an integer, which is then 3288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // casted to a pointer, this pessimizes pointer analysis a lot. 3291df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (SrcPTy->isPointerTy() == LI.getType()->isPointerTy()) && 3308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) == 3318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) { 3328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 3348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before the load, cast 3358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the result of the loaded value. 3366ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *NewLoad = 3378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.Builder->CreateLoad(CastOp, LI.isVolatile(), CI->getName()); 3386ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson NewLoad->setAlignment(LI.getAlignment()); 339cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman NewLoad->setAtomic(LI.getOrdering(), LI.getSynchScope()); 3408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Now cast the result of the load. 3418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return new BitCastInst(NewLoad, LI.getType()); 3428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 3468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 3478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3488d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitLoadInst(LoadInst &LI) { 3498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Op = LI.getOperand(0); 3508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Attempt to improve the alignment. 3528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD) { 3538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner unsigned KnownAlign = 354687140c818ba4b896329a83324714140b6580ef8Chris Lattner getOrEnforceKnownAlignment(Op, TD->getPrefTypeAlignment(LI.getType()),TD); 3550fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned LoadAlign = LI.getAlignment(); 3560fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned EffectiveLoadAlign = LoadAlign != 0 ? LoadAlign : 3570fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman TD->getABITypeAlignment(LI.getType()); 3580fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman 3590fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman if (KnownAlign > EffectiveLoadAlign) 3608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setAlignment(KnownAlign); 3610fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman else if (LoadAlign == 0) 3620fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman LI.setAlignment(EffectiveLoadAlign); 3638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (cast X) --> cast (load X) iff safe. 3668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<CastInst>(Op)) 3678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) 3688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 3698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 370cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // None of the following transforms are legal for volatile/atomic loads. 371cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // FIXME: Some of it is okay for atomic loads; needs refactoring. 372cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (!LI.isSimple()) return 0; 3738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple store-to-load forwarding and load CSE, to catch cases 375ab4c366274a582dd8146b2820c6b999cad5fce36Duncan Sands // where there are several consecutive memory accesses to the same location, 3768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // separated by a few arithmetic operations. 3778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &LI; 3788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Value *AvailableVal = FindAvailableLoadedValue(Op, LI.getParent(), BBI,6)) 3798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, AvailableVal); 3808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load(gep null, ...) -> unreachable 3828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(Op)) { 3838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner const Value *GEPI0 = GEPI->getOperand(0); 3848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 3858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(GEPI0) && GEPI->getPointerAddressSpace() == 0){ 3868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate 3878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // that this code is not reachable. We do this instead of inserting 3888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // an unreachable instruction directly because we cannot modify the 3898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // CFG. 3908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 3918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 3928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 3938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 3958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 3968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load null/undef -> unreachable 3978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // TODO: Consider a target hook for valid address spaces for this xform. 3988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Op) || 3998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner (isa<ConstantPointerNull>(Op) && LI.getPointerAddressSpace() == 0)) { 4008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a new store to null instruction before the load to indicate that 4018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // this code is not reachable. We do this instead of inserting an 4028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unreachable instruction directly because we cannot modify the CFG. 4038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner new StoreInst(UndefValue::get(LI.getType()), 4048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant::getNullValue(Op->getType()), &LI); 4058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return ReplaceInstUsesWith(LI, UndefValue::get(LI.getType())); 4068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Instcombine load (constantexpr_cast global) -> cast (load global) 4098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Op)) 4108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 4118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineLoadCast(*this, LI, TD)) 4128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 4138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Op->hasOneUse()) { 4158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Change select and PHI nodes to select values instead of addresses: this 4168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // helps alias analysis out a lot, allows many others simplifications, and 4178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // exposes redundancy in the code. 4188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 4198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Note that we cannot do the transformation unless we know that the 4208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // introduced loads cannot trap! Something like this is valid as long as 4218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the condition is always false: load (select bool %C, int* null, int* %G), 4228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // but it would not be valid if we transformed it to load from null 4238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // unconditionally. 4248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // 4258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SelectInst *SI = dyn_cast<SelectInst>(Op)) { 4268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (Cond, &V1, &V2)) --> select(Cond, load &V1, load &V2). 42749db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson unsigned Align = LI.getAlignment(); 42849db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson if (isSafeToLoadUnconditionally(SI->getOperand(1), SI, Align, TD) && 42949db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson isSafeToLoadUnconditionally(SI->getOperand(2), SI, Align, TD)) { 4306ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V1 = Builder->CreateLoad(SI->getOperand(1), 43149db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(1)->getName()+".val"); 4326ecfccfd55274187368b86d7f2e65f77d1921c36Bob Wilson LoadInst *V2 = Builder->CreateLoad(SI->getOperand(2), 43349db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson SI->getOperand(2)->getName()+".val"); 43449db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V1->setAlignment(Align); 43549db68fba01722ca032dc5170f8248a9d25f0199Bob Wilson V2->setAlignment(Align); 4368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return SelectInst::Create(SI->getCondition(), V1, V2); 4378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, null, P)) -> load P 4408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(1))) 4418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 4428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(2)); 4438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 4448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // load (select (cond, P, null)) -> load P 4478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Constant *C = dyn_cast<Constant>(SI->getOperand(2))) 4488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (C->isNullValue()) { 4498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner LI.setOperand(0, SI->getOperand(1)); 4508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return &LI; 4518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 4558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 4568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// InstCombineStoreToCast - Fold store V, (cast P) -> store (cast V), P 4588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// when possible. This makes it generally easy to do alias analysis and/or 4598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SROA/mem2reg of the memory object. 4608d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic Instruction *InstCombineStoreToCast(InstCombiner &IC, StoreInst &SI) { 4618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner User *CI = cast<User>(SI.getOperand(1)); 4628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *CastOp = CI->getOperand(0); 4638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 464db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *DestPTy = cast<PointerType>(CI->getType())->getElementType(); 465db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner PointerType *SrcTy = dyn_cast<PointerType>(CastOp->getType()); 4668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SrcTy == 0) return 0; 4678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 468db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type *SrcPTy = SrcTy->getElementType(); 4698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4701df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!DestPTy->isIntegerTy() && !DestPTy->isPointerTy()) 4718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 4728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// NewGEPIndices - If SrcPTy is an aggregate type, we can emit a "noop gep" 4748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// to its first element. This allows us to handle things like: 4758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// store i32 xxx, (bitcast {foo*, float}* %P to i32*) 4768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner /// on 32-bit hosts. 4778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SmallVector<Value*, 4> NewGEPIndices; 4788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the source is an array, the code below will not succeed. Check to 4808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // see if a trivial 'gep P, 0, 0' will help matters. Only do this for 4818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // constants. 4821df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SrcPTy->isArrayTy() || SrcPTy->isStructTy()) { 4838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Index through pointer. 4848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Constant *Zero = Constant::getNullValue(Type::getInt32Ty(SI.getContext())); 4858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 4868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 4878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner while (1) { 488db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner if (StructType *STy = dyn_cast<StructType>(SrcPTy)) { 4898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!STy->getNumElements()) /* Struct can be empty {} */ 4908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 4928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = STy->getElementType(0); 493db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner } else if (ArrayType *ATy = dyn_cast<ArrayType>(SrcPTy)) { 4948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewGEPIndices.push_back(Zero); 4958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcPTy = ATy->getElementType(); 4968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 4978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 4988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 4998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy = PointerType::get(SrcPTy, SrcTy->getAddressSpace()); 5028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5041df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (!SrcPTy->isIntegerTy() && !SrcPTy->isPointerTy()) 5058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 5068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointers point into different address spaces or if they point to 5088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // values with different sizes, we can't do the transformation. 5098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!IC.getTargetData() || 5108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SrcTy->getAddressSpace() != 5118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner cast<PointerType>(CI->getType())->getAddressSpace() || 5128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(SrcPTy) != 5138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner IC.getTargetData()->getTypeSizeInBits(DestPTy)) 5148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 5158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we are casting from one integer or pointer type to another of 5178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the same size. Instead of casting the pointer before 5188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the store, cast the value to be stored. 5198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *NewCast; 5208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *SIOp0 = SI.getOperand(0); 5218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Instruction::CastOps opcode = Instruction::BitCast; 522db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastSrcTy = SIOp0->getType(); 523db125cfaf57cc83e7dd7453de2d509bc8efd0e5eChris Lattner Type* CastDstTy = SrcPTy; 5241df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (CastDstTy->isPointerTy()) { 525b0bc6c361da9009e8414efde317d9bbff755f6c0Duncan Sands if (CastSrcTy->isIntegerTy()) 5268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::IntToPtr; 5271df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands } else if (CastDstTy->isIntegerTy()) { 5281df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands if (SIOp0->getType()->isPointerTy()) 5298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner opcode = Instruction::PtrToInt; 5308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // SIOp0 is a pointer to aggregate and this is a store to the first field, 5338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // emit a GEP to index into its first field. 5348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!NewGEPIndices.empty()) 5350a2a60ace9b79164b71794ce7ff981171c61e442Jay Foad CastOp = IC.Builder->CreateInBoundsGEP(CastOp, NewGEPIndices); 5368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner NewCast = IC.Builder->CreateCast(opcode, SIOp0, CastDstTy, 5388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SIOp0->getName()+".c"); 53917a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman SI.setOperand(0, NewCast); 54017a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman SI.setOperand(1, CastOp); 54117a0bf996fb61cdd43cec2cfc7db53145bbc767aDan Gohman return &SI; 5428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 5438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// equivalentAddressValues - Test if A and B will obviously have the same 5458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// value. This includes recognizing that %t0 and %t1 will have the same 5468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// value in code like this: 5478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t0 = getelementptr \@a, 0, 3 5488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// store i32 0, i32* %t0 5498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t1 = getelementptr \@a, 0, 3 5508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// %t2 = load i32* %t1 5518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 5528d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerstatic bool equivalentAddressValues(Value *A, Value *B) { 5538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Test if the values are trivially equivalent. 5548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (A == B) return true; 5558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Test if the values come form identical arithmetic instructions. 5578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // This uses isIdenticalToWhenDefined instead of isIdenticalTo because 5588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // its only used to compare two uses within the same basic block, which 5598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // means that they'll always either have the same value or one of them 5608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // will have an undefined value. 5618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<BinaryOperator>(A) || 5628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<CastInst>(A) || 5638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<PHINode>(A) || 5648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner isa<GetElementPtrInst>(A)) 5658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *BI = dyn_cast<Instruction>(B)) 5668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (cast<Instruction>(A)->isIdenticalToWhenDefined(BI)) 5678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return true; 5688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise they may not be equivalent. 5708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 5718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 5728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5738d9b8d717e665945b31b0742b901561fb433ceceChris LattnerInstruction *InstCombiner::visitStoreInst(StoreInst &SI) { 5748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Val = SI.getOperand(0); 5758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *Ptr = SI.getOperand(1); 5768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 5778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Attempt to improve the alignment. 5788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (TD) { 5798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner unsigned KnownAlign = 580687140c818ba4b896329a83324714140b6580ef8Chris Lattner getOrEnforceKnownAlignment(Ptr, TD->getPrefTypeAlignment(Val->getType()), 581687140c818ba4b896329a83324714140b6580ef8Chris Lattner TD); 5820fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned StoreAlign = SI.getAlignment(); 5830fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman unsigned EffectiveStoreAlign = StoreAlign != 0 ? StoreAlign : 5840fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman TD->getABITypeAlignment(Val->getType()); 5850fd353376b2741fc477c5fe05a5f18ae3abc4f60Dan Gohman 5860ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling if (KnownAlign > EffectiveStoreAlign) 5878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setAlignment(KnownAlign); 5880ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling else if (StoreAlign == 0) 5890ccae0b1f6b95e4500adb45649472389a1f111a7Bill Wendling SI.setAlignment(EffectiveStoreAlign); 5908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 5918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 592cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // Don't hack volatile/atomic stores. 593cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // FIXME: Some bits are legal for atomic stores; needs refactoring. 594cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (!SI.isSimple()) return 0; 595cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman 596cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // If the RHS is an alloca with a single use, zapify the store, making the 597cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // alloca dead. 598cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (Ptr->hasOneUse()) { 599cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (isa<AllocaInst>(Ptr)) 600cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman return EraseInstFromFunction(SI); 601cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) { 602cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (isa<AllocaInst>(GEP->getOperand(0))) { 603cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (GEP->getOperand(0)->hasOneUse()) 604cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman return EraseInstFromFunction(SI); 605cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 606cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 607cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman } 608cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman 6098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Do really simple DSE, to catch cases where there are several consecutive 6108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // stores to the same location, separated by a few arithmetic operations. This 6118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // situation often occurs with bitfield accesses. 6128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = &SI; 6138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (unsigned ScanInsts = 6; BBI != SI.getParent()->begin() && ScanInsts; 6148d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --ScanInsts) { 6158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 61629fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // Don't count debug info directives, lest they affect codegen, 61729fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez // and we skip pointer-to-pointer bitcasts, which are NOPs. 61829fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez if (isa<DbgInfoIntrinsic>(BBI) || 6191df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 6208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ScanInsts++; 6218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 6228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6238d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6248d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreInst *PrevSI = dyn_cast<StoreInst>(BBI)) { 6258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Prev store isn't volatile, and stores to the same location? 626cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman if (PrevSI->isSimple() && equivalentAddressValues(PrevSI->getOperand(1), 627cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getOperand(1))) { 6288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++NumDeadStore; 6298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 6308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*PrevSI); 6318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner continue; 6328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 6348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this is a load, we have to stop. However, if the loaded value is from 6378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the pointer we're loading and is producing the pointer we're storing, 6388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // then *this* store is dead (X = load P; store X -> P). 6398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (LoadInst *LI = dyn_cast<LoadInst>(BBI)) { 640948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang if (LI == Val && equivalentAddressValues(LI->getOperand(0), Ptr) && 641cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman LI->isSimple()) 642948d9e7ec7c4f8da50d2640d3564b01d40ffd4b1Jin-Gu Kang return EraseInstFromFunction(SI); 6438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, this is a load from some other location. Stores before it 6458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // may not be dead. 6468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 6478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6498d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Don't skip over loads or things that can modify memory. 6508d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayWriteToMemory() || BBI->mayReadFromMemory()) 6518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 6528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store X, null -> turns into 'unreachable' in SimplifyCFG 6558d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<ConstantPointerNull>(Ptr) && SI.getPointerAddressSpace() == 0) { 6568d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!isa<UndefValue>(Val)) { 6578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner SI.setOperand(0, UndefValue::get(Val->getType())); 6588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *U = dyn_cast<Instruction>(Val)) 6598d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Worklist.Add(U); // Dropped a use. 6608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // Do not modify these! 6628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 6638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // store undef, Ptr -> noop 6658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<UndefValue>(Val)) 6668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return EraseInstFromFunction(SI); 6678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the pointer destination is a cast, see if we can fold the cast into the 6698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // source instead. 6708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (isa<CastInst>(Ptr)) 6718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 6728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 6738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) 6748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (CE->isCast()) 6758d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (Instruction *Res = InstCombineStoreToCast(*this, SI)) 6768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return Res; 6778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If this store is the last instruction in the basic block (possibly 680a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // excepting debug info instructions), and if the block ends with an 681a4c77622f7f9f7546f0eae7c171ab56df125dc9aVictor Hernandez // unconditional branch, try to move it to the successor block. 6828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI = &SI; 6838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner do { 6848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner ++BBI; 68529fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez } while (isa<DbgInfoIntrinsic>(BBI) || 6861df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())); 6878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BranchInst *BI = dyn_cast<BranchInst>(BBI)) 6888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BI->isUnconditional()) 6898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (SimplifyStoreAtEndOfBlock(SI)) 6908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; // xform done! 6918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return 0; 6938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 6948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 6958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// SimplifyStoreAtEndOfBlock - Turn things like: 6968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// if () { *P = v1; } else { *P = v2 } 6978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 6988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 6998d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// Simplify things like: 7008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// *P = v1; if () { *P = v2; } 7018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// into a phi node with a store in the successor. 7028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner/// 7038d9b8d717e665945b31b0742b901561fb433ceceChris Lattnerbool InstCombiner::SimplifyStoreAtEndOfBlock(StoreInst &SI) { 7048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *StoreBB = SI.getParent(); 7058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if the successor block has exactly two incoming edges. If 7078d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // so, see if the other predecessor contains a store to the same location. 7088d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if so, insert a PHI node (if needed) and move the stores down. 7098d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *DestBB = StoreBB->getTerminator()->getSuccessor(0); 7108d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7118d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Determine whether Dest has exactly two predecessors and, if so, compute 7128d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // the other predecessor. 7138d9b8d717e665945b31b0742b901561fb433ceceChris Lattner pred_iterator PI = pred_begin(DestBB); 714a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif BasicBlock *P = *PI; 7158d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock *OtherBB = 0; 716a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 717a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) 718a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 719a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif 720a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (++PI == pred_end(DestBB)) 7218d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7228d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 723a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif P = *PI; 724a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif if (P != StoreBB) { 7258d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBB) 7268d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 727a9b8338bfa126de7ad6d57ca417b39d5c6a979ffGabor Greif OtherBB = P; 7288d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 7298d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (++PI != pred_end(DestBB)) 7308d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7318d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7328d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Bail out if all the relevant blocks aren't distinct (this can happen, 7338d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // for example, if SI is in an infinite loop) 7348d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (StoreBB == DestBB || OtherBB == DestBB) 7358d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7368d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7378d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Verify that the other block ends in a branch and is not otherwise empty. 7388d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BasicBlock::iterator BBI = OtherBB->getTerminator(); 7398d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BranchInst *OtherBr = dyn_cast<BranchInst>(BBI); 7408d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherBr || BBI == OtherBB->begin()) 7418d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7428d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7438d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If the other block ends in an unconditional branch, check for the 'if then 7448d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // else' case. there is an instruction before the branch. 7458d9b8d717e665945b31b0742b901561fb433ceceChris Lattner StoreInst *OtherStore = 0; 7468d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->isUnconditional()) { 7478d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 7488d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Skip over debugging info. 74929fa5e98863332eb808a6f5c1e29138ca6fd7f5cVictor Hernandez while (isa<DbgInfoIntrinsic>(BBI) || 7501df9859c40492511b8aa4321eb76496005d3b75bDuncan Sands (isa<BitCastInst>(BBI) && BBI->getType()->isPointerTy())) { 7518d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI==OtherBB->begin()) 7528d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7538d9b8d717e665945b31b0742b901561fb433ceceChris Lattner --BBI; 7548d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 755cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // If this isn't a store, isn't a store to the same location, or is not the 756cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman // right kind of store, bail out. 7578d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherStore = dyn_cast<StoreInst>(BBI); 7588d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (!OtherStore || OtherStore->getOperand(1) != SI.getOperand(1) || 759cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman !SI.isSameOperationAs(OtherStore)) 7608d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7618d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } else { 7628d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Otherwise, the other block ended with a conditional branch. If one of the 7638d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // destinations is StoreBB, then we have the if/then case. 7648d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherBr->getSuccessor(0) != StoreBB && 7658d9b8d717e665945b31b0742b901561fb433ceceChris Lattner OtherBr->getSuccessor(1) != StoreBB) 7668d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7678d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7688d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Okay, we know that OtherBr now goes to Dest and StoreBB, so this is an 7698d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // if/then triangle. See if there is a store to the same ptr as SI that 7708d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // lives in OtherBB. 7718d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (;; --BBI) { 7728d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Check to see if we find the matching store. 7738d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if ((OtherStore = dyn_cast<StoreInst>(BBI))) { 7748d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (OtherStore->getOperand(1) != SI.getOperand(1) || 775cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman !SI.isSameOperationAs(OtherStore)) 7768d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7778d9b8d717e665945b31b0742b901561fb433ceceChris Lattner break; 7788d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 7798d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // If we find something that may be using or overwriting the stored 7808d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // value, or if we run out of instructions, we can't do the xform. 7818d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (BBI->mayReadFromMemory() || BBI->mayWriteToMemory() || 7828d9b8d717e665945b31b0742b901561fb433ceceChris Lattner BBI == OtherBB->begin()) 7838d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7848d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 7858d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7868d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // In order to eliminate the store in OtherBr, we have to 7878d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // make sure nothing reads or overwrites the stored value in 7888d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // StoreBB. 7898d9b8d717e665945b31b0742b901561fb433ceceChris Lattner for (BasicBlock::iterator I = StoreBB->begin(); &*I != &SI; ++I) { 7908d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // FIXME: This should really be AA driven. 7918d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (I->mayReadFromMemory() || I->mayWriteToMemory()) 7928d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return false; 7938d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 7948d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 7958d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 7968d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Insert a PHI node now if we need it. 7978d9b8d717e665945b31b0742b901561fb433ceceChris Lattner Value *MergedVal = OtherStore->getOperand(0); 7988d9b8d717e665945b31b0742b901561fb433ceceChris Lattner if (MergedVal != SI.getOperand(0)) { 7993ecfc861b4365f341c5c969b40e1afccde676e6fJay Foad PHINode *PN = PHINode::Create(MergedVal->getType(), 2, "storemerge"); 8008d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(SI.getOperand(0), SI.getParent()); 8018d9b8d717e665945b31b0742b901561fb433ceceChris Lattner PN->addIncoming(OtherStore->getOperand(0), OtherBB); 8028d9b8d717e665945b31b0742b901561fb433ceceChris Lattner MergedVal = InsertNewInstBefore(PN, DestBB->front()); 8038d9b8d717e665945b31b0742b901561fb433ceceChris Lattner } 8048d9b8d717e665945b31b0742b901561fb433ceceChris Lattner 8058d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Advance to a place where it is safe to insert the new store and 8068d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // insert it. 8075b6f42f57e730c2d968c313a27fa505a3c3e5efaBill Wendling BBI = DestBB->getFirstInsertionPt(); 808a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman StoreInst *NewSI = new StoreInst(MergedVal, SI.getOperand(1), 809cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.isVolatile(), 810cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getAlignment(), 811cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getOrdering(), 812cc4a0435b7ee34af2c64a6f7ee63642f56096d1bEli Friedman SI.getSynchScope()); 813a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman InsertNewInstBefore(NewSI, *BBI); 814a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman NewSI->setDebugLoc(OtherStore->getDebugLoc()); 815a311c34d2af7c750f016ef5e4c41bee77a1dfac7Eli Friedman 8168d9b8d717e665945b31b0742b901561fb433ceceChris Lattner // Nuke the old stores. 8178d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(SI); 8188d9b8d717e665945b31b0742b901561fb433ceceChris Lattner EraseInstFromFunction(*OtherStore); 8198d9b8d717e665945b31b0742b901561fb433ceceChris Lattner return true; 8208d9b8d717e665945b31b0742b901561fb433ceceChris Lattner} 821